Feature request: expose libvips maplut operation to map pixel values (for e.g. colour grading)

I'm interested in being able to apply 3D LUTs to images on the fly, eg. .cube files. I think vips_maplut() is the right function under the hood for this, perhaps I'll need to figure out how to generate LUT images from those files first though.

I've been trying to use some node libraries to do this, extracting the pixels as an ndarray, applying the LUT, then saving the modified pixels back to an image buffer but it's super slow and error prone (truncated image data etc).

If it's not something that makes sense for sharp no worries, hopefully I can find info on transforming an image as a readableStream assuming that's doable :)

Start by reviewing sharp's existing image-operation API and the libvips vips_maplut operation, using .cube LUT files as the input case. Define how LUT data should be represented and exposed through sharp; done means a practical API for applying a 3D LUT without manual pixel extraction.